The present invention relates generally to the implanting of orthopedic prostheses for replacing portions of skeletal joints, and more particularly, to surgical instruments and their use in preparing bones to receive implantable orthopedic prostheses.
Implant able orthopedic prostheses, in one form, comprise man-made replacements for the ends and articulating surfaces of the bones of the skeleton. Such prostheses are implanted to repair or reconstruct all or part of an articulating skeletal joint that is functioning abnormally due to disease, trauma, or congenital defects. Among the various articulating skeletal joints of the human body, for example, that are eligible to be fitted with implantable orthopedic prostheses, the knee, hip, and shoulder joints are often beneficial recipients.
The hip and knee joints play an important role in ambulation, and the shoulder joint plays an important role in manual dexterity. This results in great demand for surgical correction of abnormalities in these joints, and the ability to correct such abnormalities can have an important affect on the quality of life.
As used herein, the words proximal and distal are terms of reference that indicate a particular portion of a bone or prosthesis component according to the relative disposition of the natural bone or implanted prosthesis. Proximal indicates that portion of a component nearest the torso, whereas distal indicates that portion of a component farthest from the torso.
In a variety of implantation procedures, the bone receiving a prosthetic component is initially prepared for receipt of that component. For example, certain prosthetic components include a stem and an expanded boss that are placed into the medullary canal of the subject bone, e.g., the proximal end of a tibia prepared for receipt of a prosthetic knee joint component having a stem and a tibial boss. Preparation of the bone includes reaming the medullary canal to a size and shape able to receive the stem and expanded boss of the prosthetic component. This surrounding bone tissue supports the prosthetic component.
Prior to insertion of the stem, a trial stem is inserted into the reamed region to ensure a proper fit of the prosthetic component. In some procedures, the trial stem remains in the reamed cavity during additional cuts that are made to properly shape the bone. In fact, the trial stem can be used to support cutting instruments utilized in shaping the end of the bone for receipt of the prosthetic component.
In some cases, disease, congenital defect, or trauma can create voids in the bone tissue at a location where bone tissue is required to support the implant component. For example, certain degenerative diseases can lead to the formation of a cavity at the proximal end of the tibia or at other joint locations that could benefit from the implantation of a prosthetic device. Such voids, whether cavity or non-cavity voids, must be repaired in such a manner that will allow tissue to attach to the component and provide support for the prosthetic component.
A variety of bone replacement materials, such as allograft bone, autograft bone, bone graft substitutes, bone matrix, and suitable biological products may be used to repair voids or other defects in the bone tissue. The bone replacement material is impacted into the contained or uncontained defect to bond with and support the implanted prosthetic component. During this impaction procedure, it would be desirable to prevent the impacted bone from falling into the medullary canal or other areas that will be occupied by the prosthetic component upon implantation. It also would be desirable to provide for proper formation of the bone replacement material so as to accommodate receipt of the prosthetic component.
The present invention provides a technique for preparing a bone to receive an implantable orthopedic prosthesis. In one embodiment, the technique comprises the use of a bone impaction preform to hold the shape of an implantable component during impaction of the bone replacement material. In this embodiment, the bone impaction preform is a modular component that may be selectively coupled and uncoupled with a trial stem and/or a trial stem adapter.
In modular form, a variety of bone impaction preforms and trial stems can be combined according to the type and size of the joint being prepared for receipt of an implantable orthopedic prosthesis. With this modularity, a relatively small number of trial stems and modular preforms can be combined in a relatively large number of configurations. In one exemplary application of the present technique, a practitioner selects a desired combination of a modular trial stem in a modular preform. The inner region or medullary canal of a bone is then reamed to sufficient size to accommodate the stem of an implantable prosthetic component. The modular trial stem is moved into the reamed canal until the modular preform is at least partially positioned within the void to be prepared. Once positioned, bone replacement material is readily packed around the modular preform. The modular preform prevents bone replacement material from falling into the medullary canal while holding the shape of the component to be implanted.